I have successfully used High Voltage Digital Servos with the Cortex (such as HITEC HS-5665MH). The Cortex PWM ports output the battery voltage. A normal hobby servo is only rated at 5V. The extra voltage on the PWM port can damage a regular hobby servo. A high voltage servo is intended for use with 6 NiCd or NiMH cells or 2 LiPo cells.